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Because in a belly landing the engine and prop would be turning at minimum power, if not at idle, the prop would be out of its governing range, and if the pilot had any sense at all, he would have killed the engine just before touch down and the prop would be wind milling down at time of impact. This would mean minimum stress on the entire drivetrain when the prop starts hitting the ground, especially since the high wing loading in a power off condition would result in a nose high touchdown so the prop blades get curled inward from the tips in a series of glancing blows instead of a single blade sudden stop.If that were a problem, then why don't we see P-39s that belly landed torn up by driveshafts whipping around?
It's hard to find graphs for certain aircraft, isn't it?I can't take credit for the graph, as I found it in the Wisconsin State Historical Library nearly 50 years ago! Been looking for performance graphs ever since. Found Nirvana with AHT. Mike Williams and Neil Sterlings web site and TAIC manuals.
Because in a belly landing the engine and prop would be turning at minimum power, if not at idle, the prop would be out of its governing range, and if the pilot had any sense at all, he would have killed the engine just before touch down and the prop would be wind milling down at time of impact. This would mean minimum stress on the entire drivetrain when the prop starts hitting the ground, especially since the high wing loading in a power off condition would result in a nose high touchdown so the prop blades get curled inward from the tips in a series of glancing blows instead of a single blade sudden stop.
Wasn't there a rumor that the vibration from the drive shaft in the P-39 would make the pilot impotent?
The infamous "buzz balls" theory.Wasn't there a rumor that the vibration from the drive shaft in the P-39 would make the pilot impotent?
The point I've been making all along. Now convince our favorite Ex-spurt.Maybe that's why that isolated forward gearbox was armored, some failure modes of it could be catastrophic .
Okay, you convinced me.The point I've been making all along. Now convince our favorite Ex-spurt.
If you get a bullet through the propeller blade, it would depend on what size bullet, either a hole with a whistle and slight imbalance, keep flying.I'm having a hard time biting on the driveshaft issue. First, while I haven't read much about the P-39, and, while there are a lot of complaints about flying the plane, driveshaft issues and failures does not seem to pop up much. And this issue of getting a bullet through it causing catastrophic failures, how about a bullet or shell through a propeller blade, or hub, a fuel line, the pilot, or a control line. In wartime, an aircraft is not a safe place to be.
I've circle track raced for over 20 years, I've seen a loose drive shaft, from a broken back u-joint, flip a 3500 lb car instantly.
That's why most car racing associations require driveshaft hoops, front and rear, made from 1/4 in. steel.
From "Short Stirling, The First of the RAF Heavy Bombers – Pino Lombardi"On the Short Stirling
I'm not really all that knowledgeable on the Shorts Stirling, but I'm not sure what you mean by the 9000 + pounds of "good ideas" from the Air Ministry.
As for the larger wingspan, I thought they reduced that because of the need to fit it in the hangars?
Shorts were constantly bombarded with 'minor' alterations to the original design. At one stage over 150 modifications had been requested; one was a requirement to carry small 50-lb bombs along the trailing edges of the wings.
During early 1939, the all up weight of the Stirling had risen by some 9,000 lbs and was still creeping up doe to extra equipment required by the Air Ministry.
P-39 Expert
Attached is a graph for the P-39D-2, powered by the Allison V-1710 E-6 (Military designation V-1710-63).
For your use and information.
Eagledad
View attachment 608389
Wouldn't that be a front U joint, which would act like a pole vault pole as the shaft dropped and dug in?
Because in a belly landing the engine and prop would be turning at minimum power, if not at idle, the prop would be out of its governing range, and if the pilot had any sense at all, he would have killed the engine just before touch down and the prop would be wind milling down at time of impact. This would mean minimum stress on the entire drivetrain when the prop starts hitting the ground, especially since the high wing loading in a power off condition would result in a nose high touchdown so the prop blades get curled inward from the tips in a series of glancing blows instead of a single blade sudden stop.
Wouldn't that be a front U joint, which would act like a pole vault pole as the shaft dropped and dug in?
The race car didn't have the heavy bearings bolted onto the frame the way the P-39 did. The race car's drive shaft has to take suspension movement into account. The P-39 didn't have universal joints.
Back in the 80's, I saw a Pro-street Charger blow his pumpkin on the launch and the driveshaft ripped free of the loops, launching it sideways through the fence and into the crowd.No in this particular case it was the rear u-joint, it hit the pavement hard enough to turn the car over, then the driveshaft slide out.
The front U-joint was still on the shaft, the rear broken U-joint half was still on the rear end.
Though I've seen it happen more often the way you describe.
After a few years of those types of mishaps, they started requiring drive shaft hoops on all RWD cars, no matter how little HP they have.
The rear U-joint breaking is by far the most destructive of the 2 failure modes.